I have done a great activity for the last few years which is really engaging. However, it takes 2 days to complete.
Students are placed in small groups and then are given the job of creating an updated juice container that is a rectangular prism to fit better in a child's lunch box. They are given a minimum volume in cc's and must decide the best dimension to use for the juice box. They then create a net for their box (card stock with cm grid printed on it), decorate it and construct the box.
I've attached my assignment document to the post.
This is adapted from this site: http://www.learnnc.org/lp/pages/3497